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Flavor Investigator: Pistachio

Pistachios are a biblical nut and I am not basing this statement on their amazing flavour. Pistachios are mentioned in the Old Testament in Genesis 43:11, “Then their father Israel said to them, “If it must be, then do this: Put some of the best products of the land in your bags and take them down to the man as a gift–a little balm and a little honey, some spices and myrrh, some pistachio nuts and almonds.” I think we can attest that the pistachio has been around for a long time.

Pistachios (Pistacia vera) come from the Anacardiaceae family. This family is more commonly known as the cashew family meaning that pistachios are not actually nuts but seeds. The pistachio tree produces drupes which contain an elongated seed. The fruit has the appearance of small plums with a yellow-reddish colour. The outer skin is than removed to produce the characteristic brown-coloured exterior shell you are familiar with. Within this shell is a seed, the edible portion which we consume. During the maturation process the seed will change colour from green to a distinctive yellow/red colour. Furthermore, during the pistachio maturation process the shell will open making a noisy “pop.” This process is known as dehiscence lettings producers know the seed is ready for human consumption.

Pistachio Chemical Composition and Drying/Roasting

As it would be suspected pistachios contain a slew of different components. These components include unsaturated fatty acids, protein, dietary fiber, magnesium, potassium and polyphenols. Compared to almonds and walnuts have lower fat and higher levels or potassium. During processing however pistachios are dried as it increases safety and allows for longer shelf life. As a result, drying alters the composition of pistachios such as sun drying which reduced the total polyphenol levels. It is suggested that higher drying temperatures will affect sensory parameters. Roasting on the other hand directly affects sensory characteristics as it initiates the Maillard reaction and lipid oxidation in pistachio oil. In particular, roasted pistachios have higher amounts of alpha-Pinene and 3-carene.

Flavour Compounds Present in Pistachios

When scientist performed a chemical analysis of Turkish pistachios they found the oils contained about 89.67% monoterpenes, 8.1% oxygenated monoterpenes and 1.2% diterpenes. If you are not aware monoterepenes widely occur in nature and are primary contributors to smells associated with herbs, spices and fruits. In pistachios alpha-Pinene is the dominant terpene, it taste at a 5.00-100.00ppm concentration is described as being intensely woody, piney and terpy with apparent notes of camphoraceous and turpentine. Found at a much lower levels is beta-pinene, it has a flavour profile similar to that of the alpha form. It is described as fresh, piney, terpy and resinous with a slight minty, camphoraceous and spicy nuance.